Although the above procedure is noisy and can result in adding
terms to \(Q_i\)  that are non-relevant, or adding too few relevant terms \(Q_i\) , [1]} report good performance on the TREC CAsT 2019 dataset, where the majority of expansion terms in the oracle manual de-contextualized queries (see the example in Table REF ) are indeed from the previous query turns. However, it remains to be validated whether the observation and good performance hold on other conversational search benchmarks or in real-world scenarios.
